Process for the production of an automotive oem multi-layer coating

Abstract

A process for the production of an automotive OEM multi-layer coating, includes, but is not limited to applying a base coat layer onto an automotive substrate, applying a clear top coat layer onto the base coat layer, and jointly curing the base coat and clear top coat layers. The base coat layer is applied from a modified water-borne base coat produced by mixing an unmodified water-borne base coat with a polyisocyanate crosslinker component making use of a static mixer, and wherein the polyisocyanate crosslinker component comprises at least one polyisocyanate crosslinker and γ-butyrolactone as water-miscible solvent.

1 . A process for the production of an automotive OEM multi-layer coating, comprising:
 applying a base coat layer onto an automotive substrate;   applying a clear top coat layer onto the base coat layer; and   jointly curing the base coat and clear top coat layers,   
       wherein the base coat layer is applied from a modified water-borne base coat produced by mixing an unmodified water-borne base coat with a polyisocyanate crosslinker component making use of a static mixer, and wherein the polyisocyanate crosslinker component comprises at least one polyisocyanate crosslinker and γ-butyrolactone as water-miscible solvent. 
     
     
         2 . The process of  claim 1 , wherein between the application of the modified water-borne base coat and the clear top coat an additional coating layer is applied from the unmodified water-borne base coat. 
     
     
         3 . The process of  claim 1 , wherein the mixing ratio for the preparation of the modified water-borne base coat lies in the range of approximately 0.05 to approximately 0.3 pbw of polyisocyanate crosslinker component:approximately 1 pbw of unmodified water-borne base coat. 
     
     
         4 . The process of  claim 1 , wherein the unmodified water-borne base coat comprises a resin solids content with a hydroxyl value in the range of approximately 5 to approximately 120 mg KOH/g. 
     
     
         5 . The process of  claim 1 , wherein the polyisocyanate crosslinker component comprises approximately 50 to approximately 90 wt. % of the at least one polyisocyanate crosslinker and approximately 10 to approximately 50 wt. % of γ-butyrolactone. 
     
     
         6 . The process of  claim 1 , wherein the total isocyanate content of the at least one polyisocyanate crosslinker is in the range of approximately 2 to approximately 40 wt. % (calculated as NCO). 
     
     
         7 . The process of  claim 1 , wherein the at least one polyisocyanate crosslinker comprises one or more polyisocyanates with aliphatically attached isocyanate groups. 
     
     
         8 . The process of  claim 1 , wherein the polyisocyanate crosslinker component comprises up to approximately 20 wt. % of organic solvent(s) inert towards free isocyanate and other than γ-butyrolactone. 
     
     
         9 . The process of  claim 1 , wherein the polyisocyanate crosslinker component comprises γ-butyrolactone as the only organic solvent. 
     
     
         10 . The process of  claim 1 , wherein the polyisocyanate crosslinker component comprises approximately 50 to approximately 90 wt. % of the at least one polyisocyanate crosslinker, approximately 10 to approximately 50 wt. % of γ-butyrolactone, approximately 0 to approximately 20 wt. % of organic solvents inert towards free isocyanate and other than γ-butyrolactone, and approximately 0 to approximately 10 wt. % of at least one additive. 
     
     
         11 . The process of  claim 1 , wherein the polyisocyanate crosslinker component consists of approximately 50 to approximately 90 wt. % of the at least one polyisocyanate crosslinker, approximately 10 to approximately 50 wt. % of γ-butyrolactone, approximately 0 to approximately 20 wt. % of organic solvents inert towards free isocyanate and other than γ-butyrolactone, and approximately 0 to approximately 10 wt. % of at least one additive, wherein the sum of the wt. % totals approximately 100 wt. %. 
     
     
         12 . The process of  claim 1 , wherein the polyisocyanate crosslinker component consists of approximately 50 to approximately 90 wt. % of the at least one polyisocyanate crosslinker and approximately 10 to approximately 50 wt. % of γ-butyrolactone, wherein the sum of the wt. % totals approximately 100 wt. %. 
     
     
         13 . The process of  claim 6 , wherein the polyisocyanate crosslinker component comprises approximately 50 to approximately 90 wt. % of the at least one polyisocyanate crosslinker, approximately 10 to approximately 50 wt. % of γ-butyrolactone, approximately 0 to approximately 20 wt. % of organic solvents inert towards free isocyanate and other than γ-butyrolactone, and approximately 0 to approximately 10 wt. % of at least one additive. 
     
     
         14 . The process of  claim 6 , wherein the polyisocyanate crosslinker component consists of approximately 50 to approximately 90 wt. % of the at least one polyisocyanate crosslinker, approximately 10 to approximately 50 wt. % of γ-butyrolactone, approximately 0 to approximately 20 wt. % of organic solvents inert towards free isocyanate and other than γ-butyrolactone, and approximately 0 to approximately 10 wt. % of at least one additive, wherein the sum of the wt. % totals approximately 100 wt. %. 
     
     
         15 . The process of  claim 6 , wherein the polyisocyanate crosslinker component consists of approximately 50 to approximately 90 wt. % of the at least one polyisocyanate crosslinker and approximately 10 to approximately 50 wt. % of γ-butyrolactone, wherein the sum of the wt. % totals approximately 100 wt. %. 
     
     
         16 . The process of  claim 1 , wherein the at least one polyisocyanate crosslinker comprises one or more polyisocyanates with cycloaliphatically attached isocyanate groups. 
     
     
         17 . The process of  claim 1 , wherein the at least one polyisocyanate crosslinker comprises one or more polyisocyanates with araliphatically attached isocyanate groups.